In the preparation of powder metals a ball mill can contains the bulk metal and a powderizing media typically a quantity of hardened spherical balls. The powderizing media converts the bulk metal to powder form when the ball mill can is repeatedly tumbled or rotated in a specifically designed and regulated process.
Ball mill cans are made in varying sizes and of various materials. Typically, a ball mill can is cylindrical having a solid bottom end wall opposite a top end wall which includes a closure device specifically designed to contain the metal powders and media within the ball mill can.
The ball mill can is tumbled or rotated using a ball mill stand. The ball mitt stand includes a number of rotationally driven rollers onto which the ball mill can is positioned :and supported. A circumferential side wall of the ball mill can is positioned atop the rollers such that a longitudinal axis of the ball mill can is generally parallel to the underlying rollers.
The use of the ball mill stand as described for varying sizes of ball mill cans has led to a time consuming practice of centering or modifying the position of the ball mill can on the rollers so that the ball mill can does not contact or rub the stationary surfaces of the ball mill stand. Frictional contact between the stationary surfaces of the ball mill stand and the ball mill can during the milling process is a problem because it leads to the wear and degradation of the ball mill can and the ball mill stand, thereby lessening the useful life of each,
In addition to the need to avoid the frictional contact between the ball mill can and the stand, the ball mill can must be accurately positioned and centered on the rollers to avoid shifting of the ball mill can during the milling process which could lead to a deviation in the milling process and the resulting powder metal.
Prior solutions to the problem of using various sizes of ball mill cans on a ball mill stand include securing a section of channel or angle metal to the stand to position the can atop the rollers. The section of angle metal may or may not include a Teflon facing. However, the continuous frictional contact between the ball mill can and the angle metal during the milling process caused wear to the ball mill can as well as the positioning angle metal thereby shortening the life of each component. Furthermore, the rubbing contact between the ball mill can and the angle metal causes a variation in the rotational speed of the ball mill can which introduces possible milling process deviation. Therefore, the use of an angle metal secured to the ball mill stand has proven to be inadequate.
Another previous solution to the problem of positioning the ball mill can atop the rollers was for the operator to layer masking tape in various locations on the circumference of the ball mill can. Alternatively, large rubber bands placed in various locations on the ball mill can circumference have been used to position the can. The disadvantage of these approaches is that they require approximately ten minutes of operator time to accurately position the ball mill can, This increased operator time devoted to positioning the ball mill can results in increased downtime and inefficiency in the milling process. The increased operator time likewise increases the cost of the milling process in preparation of powder metals.
As evidenced by the above background, a need exists for an automatic positioning device for a ball mill can used on a ball mill stand in the preparation of powder metals. Particularly, the positioning device for the ball mill can should be automatic or require little or no operator time and be applicable for various sizes of ball mill cans and avoid the degradation or wearing away of the ball can and ball mill stand during the milling process.